In an internal combustion engine, it is known to recirculate exhaust gas from an exhaust manifold to an intake manifold. This may be performed as part of a strategy to reduce NOx emissions. Recirculating exhaust gas may be achieved by providing an exhaust gas recirculation passage between the exhaust manifold and the intake manifold. The exhaust gas recirculation passage may comprise an exhaust gas recirculation valve that controls the amount of gas that can flow in the exhaust gas recirculation passage. The exhaust gas recirculation valve may be fully closed such that no exhaust gas recirculation takes place.
Control of the exhaust gas recirculation valve may be undertaken by an engine control unit (ECU). The ECU may receive various inputs as part of a strategy that governs control of the position of the exhaust gas recirculation valve. A measured pressure differential between the exhaust manifold side of the EGR valve and the intake manifold side of the valve may be one of the inputs that is used to influence control of the position of the EGR valve.
The temperature of recirculating exhaust gas can be high. High temperatures may affect the ability of a pressure sensor to function reliably and to provide an accurate output. It is known, for this reason, to locate a pressure sensor remotely from the EGR valve on a dedicated manifold and to transfer gas pressure from either side of the EGR valve to the remotely mounted pressure sensor via transfer tubes. All of this additional hardware has an associated cost.